Various types of mulches are commonly applied over grass seed beds. The purpose of these mulches is to increase grass seed germination and decrease soil erosion to allow the seedlings to become firmly established in the seeded area. These mulches typically consist of natural materials such as straw, wood shavings, or paper. The mulches are mixed with water and agitated in a holding tank, and then sprayed onto the seed bed. Some such mulches are woven into blankets that are designed to be laid down over seed beds.
Such mulches are somewhat effective. They do absorb and retain some water, thus keeping the seed bed more hydrated then when mulch is not used. They additionally deflect some of the rain, thereby decreasing to some extent soil erosion. However, most such mulches are loose configurations of unbonded fibers that easily wash away. The paper-based mulches tend to bond into a papier mache-like mat that inhibits oxygen and sunlight transfer, and the ability of seedlings to emerge through the mulch, thus affecting the vegetation establishment.
There have also been introduced into the market chemically bonded natural fiber spray-applied mulches. These mulches use a vegetable gum binder such as guar gum to bind together natural fibers. Although this mulch is extremely well bonded, it has not been successful for a number of reasons. The chemically-bonded mulch forms an almost impenetrable layer over the seed bed that is poor at passing the needed oxygen and water through to the seed bed, and is also very difficult for the germinated seedlings to penetrate. Accordingly, the results for this product have been poor.